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D 1. E.BUCHER.- I ELECTROLYTIC AND SAPONIFYING PROCESS FOR PRODUCING NITRILE DERIVATIVES. APRLICATION FILED FEB. 23, I915- Lwmm lPatentedAug. 15,1916.

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' W 3 @QPMM JOHN E. BUCHER, 0F COVENTRY, RHODE ISLAND, ASSIGNOR Ii-0 NITROGEN PlEtOlllUC'lS COMPANY, OF PROVIDENCE, RHODE ISLAND, A CORPORATION OlF RHODE ISLAND. I

JELECTROL Y TIC AND SAPONIFYING- PROCESS FOR PRODUCING-NITRILE DERIVATIVES.

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H Application filed February 23, 1915. Serial No. 9,955.

Coventry, in the county of Kent and State of Rhode Island, have invented certain new and useful Improvements in Electrolytic and Saponifying Processes for Producingv Nitrile Derivatives," of which the following is a specification.

This invention relates to an improvedprocess by means of which oxamid may be so-che'aply and practicably produced as to permit of the use of this hitherto quite costly substance commercially for fertilizing purposes and the like. That oxamid could be produced from, for example, cyanogen by treating the latter with aldehyde was announced by von Liebig in 1860 (Ann. 113,

p. 246); and in 1867, Schmitt and Grlutz (Ben, 1, p. 66) communicated the fact that when cyanogen gas is brought into contact with aqueous concentrated hydrochloric acid, the latter at first remains colorless, but that aftertwelve hours standing, crystals of 'oxamidseparate from thecyanogen saturated acid while small quantitiesof ammonium oxalate are also formed. So far'as 1i am aware nothing further appears tohave been done looking to thepractical develop- 'ment of a process for producing oxamid either from cyanogen or a compound thereof and the object of the present invention is to provide a process whereby substantially pureloxamid can be produced on a. large scale easily and cheaply and with amini-' mum number of operations or steps. I In the drawingwhich forms a part hereof I have shown, in part diagrammatically, an

"apparatus wherein my process maybe efiectu ated.

The figure is a somewhat diagrammatic vertical median section. of an 'electrolyzing' chamber with'a tower connected thereto. I,

Herein, thefsaid chamberdesignated 1' contains a mass-2 of .acyanogen compound, such as'sodium cyanid, which is to be decomposed with liberation of cyanogen .at

thepositive pole 3. The latter may .be of graphite and is preferably inclosed as at 4' to prevent contact of the. liberated cyanogen with liberated which passes through Specification of Letters Patent.

Patented ma 15, rare.

the conduit .5, in liquid or vaporous form, t

from the electrolyzing chamber. The walls of the latter may be of cast iron and the mass to be treated therein is heated to, let us say, 550 to 600 (1., or sufiiciently to liquefy charge to the negative pole electrode, '5. 6.

the container or receptacle 1, passingthence via a lead 8. The inclosure 1 may also be of magnesia brick, or other suitable substance s upported by the container 1; the latter also resting upon insulation 9, and the electrode 3 being spaced up from the bottom of the container by means of an insulatingblock 10. The liberated cyanogen may be drawn 0% through'a conduit or pipe 11, by means of a centrifugal pump 12, or the like,

a valve 13 being provided to regulate the gaseous flow and to prevent the entrance of air to the chamber 1 when the pump is not in operation. The sodium may be collected in a condensing chamber 14-, for use in con- 1 nection with the process described in my Patent No. 1,082,845, dated December 30,

1913, for reforming cyanid' for continuing the present process.

The cyanogen leaving the pump passes preferably to the lower end of a tower or scrubber 15, similar to those used in the a m.

. monia-soda process; the towerhaving therein perforated baffies 16 through which flows preferably strongly concentrated hydrochloric acid, which may, if desired, be preheated or it may be warmed by hot cyanogen gas supplied thereto,- in order to produce the best initial results; although, as the reaction 1s strongly exothermic, the tower orv the like will in some cases have; to be cooled during the course of the operation;

a particularly advantageous way-of conducting the process herein described. The acid The receptacle landfconnections therefrom to the-tower should be air tightand enters through the pipe 17 at the upper end of the tower and acts catalytically upon the cyanogen to form oxamid according to the equation If the acid be not sufliciently cooled oxalic acid Will be formed, as follows:

the acid hence being used up with a resultant formation of ammonium chlorid, and the oxalic acid separating out as a thick crystal paste, on cooling. The solubility curves of oxalic acid and ammonium chlorid differ very greatly so that there is no difficulty in separating these products.

One mode of conducting the present process hence affords a Very cheap production of oxamid while anotheryields somewhat less cheaply but very conveniently, oxalic acid.

, Even if sufficiently cooled hydrochloric acid be not used and oxalic acid be formed, the catalyzer' may still be recovered by treating the ammonium chlorid formed with sulfuric acid to get as a by-product the commercially valuable ammonium sulfate. Oxamid is however very valuable as a fertilizer as it has nearly 32% of nitrogen and does not rea'dilylixiviate out of the soil; but it does not appear heretofore to have been so used, probably on account of its cost which until now has been practically prohibitive for this f purpose. Furthermore, as another aspect-of the present invention, commercially concentrated hydrochloric acid .of, say, sp. gr. 1.14,

' may be readily converted to stronger acid by 4p treating it with cyanogen; since the oxamid forming reaction vigorously abstracts the water from the acid. I desire to point out, however, that in order to secure results which are of highest commercial value, the acid must become saturated with cyanogen and this saturation must be maintained. It

. pressure, at 100 C., hydrochloric acid of sp.

gr. 1.18 would necessarily give off much HCl gas, thus becoming more dilute and at the same time crowding out the cyanogen gas by reducing its partial vapor pressure above the liquid. Also, the physical solubility of the cyanogen in the liquid should almost dis appear at 100 C. and under atmospheric be considered in view of the above.

pressure. If, therefore, the latter pressure he used the above factors must be more fully considered and the oxamid formation must be effected at a correspondingly lower temperature, preferably about 40 or 50 0.; since there is a distinct maximum yield of both oxamid and oxalic acid (the product or mixture of products depending upon the amount of water present in the acid, and the temperature) when operating under a determined pressure; this yield being obtainable by the use of the proper temperature corresponding to such pressure. As the cited reactions are exothermic, a rise in temperature during the course of the oxamid or oxalic acid formation is to be expected and should preferably In other words if atmospheric pressure is used, the tower or like apparatus should preferably be cooled. The oxamid precipitate obtained is usually granular and shows little if any tendency to incrust the apparatus, while the acid remaining therein evaporates 01f readily with but little decomposition of the oxamid. Even this small loss may be practically entirely avoided by distilling off the hydrochloric acid in vacuo.

I have laid emphasis in the foregoing upon the desirability of both maintaining the acid saturated and agitating the same, and the following experiment may be cited in proof thereof: A 200 cc. glass bottle containing concentrated hydrochloric acid was connected with a cyanogen gas container through the intermediacy of a burette.

Upon shaking the bottle there was a sudden rush of cyanogen thereinto until the liquid became saturated by physical absorption in from 10 to 20 seconds. As long thereafter as the shaking was continued there was a steady chemical absorption of cyanogen which was measured in the burette and this gave a very quick and accurate method of determining the rate of oxamid formation, since the saturation of the liquid catalyzer was maintained. When the shaking was stopped, the physical absorption also practically ceased, but the chemical action continued so that the liquid rapidly became unsaturated with respect to the cyanogen gas.

The bottle'was then suddenly shaken after a minute or so, when again there was a jump of water in the burette, showing that almost instantaneous absorption occurred, to make up for the unsaturation developed while the bottle was at rest. The steady chemical absorption was then allowed to proceed as before. From measurements of gas absorption, obtained in the manner just indicated, I consider that it is probable that the saturated liquid contains four or more times its volume of cyanogen and that even in such a simple apparatus, at 37 C., 15 cc. of HCl can convert its own volume, 15 cc., of syanogen gas into oxamid every minute, which is at the rate of about 3.3 grams of oxamid per hour.

By means of the above simple apparatus I have also determined that at 20 C., 15 cc. of commercial concentrated hydrochloric acid of about 1.14 sp. gr. (28 TW.) will only absorb about 1 cc. of cyanogen in 30 seconds; while acid of 1.18 sp. gr. under identically the same conditions will absorb about three times as much gas, which shows the strong retarding influence of dilution.

Hydrobromic acid, while more expensive than hydrochloric acid, is nevertheless adapted for use in the process as a catalyzer, and indeed gives even a still more rapid rate of oxamid yield. Hydriodic acid, however, while giving a still more rapid formation of oxamid is expensive, and moreover this acid is destroyed during the course of the reaction; the'iodin separating there from and contaminating the product sought. The rise in temperature of the reactive mass is also objectionably pronounced. Even when using hydrochloric acid, for example, of sp. gr. 1.14, or thereabout, if the temperature in the tower be permitted to rise unduly for the given operating pressure, whether this be atmospheric, above that of. the atmosphere, or even below, as may be found advantageous in certain cases, there is a tendency to form oxalic acid, which contaminates the oxamid produced and in addition uses up some of the catalyzer.

When conducting the operation at the room temperature, or thereabout, I prefer to introduce about 36 pounds of water with each 52 pounds of cyanogen gas entering the tower, because, as previously stated, the process steadily concentrates the hydrochloric acid by removing the water therefrom to form oxamid, and if water be not so added, either continuously or intermittently,

there would presently be given off from the tower a current of anhydrous hydrochloric acid gas while the apparatus would finally contain only solid oxamid with no liquid present, and action would cease. The water of course may be added in the form of dilute acid with the two-fold result of supplying the requisite Water to the reaction and of concentrating this dilute acid. Since the oxamid is so very slightly soluble in water or in the acid, the resultant concentrated acid is almost chemically pure. Further, constant boiling I-ICl, sp. gr. 1.13 may thus be concentrated to, say, sp. gr. 1.20, at sufficiently low temperatures or under pressure, and this acid may then be heated to drive off large volumes of HCl gas until the acid again approaches sp. gr. 1.13

after which the acid may be cooled, or introduced into the tower under pressure, and the cycle repeated. This, hence, affords a method of obtaining hydrochloric acid gas from an acid of but moderate concentration while the latter acts as a catalyzer to simultaneously form a product (oxamid) which is substantially insoluble in said catalyzer.

I may here mention that with any concentrated hydrochloric acid, if the temperature is raisedmuch above that of the room, there is a tendency to form oxalic acid as well as oxamid, and since oxalic acid is slightly decomposed at temperatures approximating 100 (1., in the presence of rela tively strong hydrochloric acid, it is preferable to operate at lower temperatures to avoid decomposition 'of the oxalic acid formed and to recover such acid by subsequent heating in cacao.

I have ascertained that diluting hydrochloric acid sp. gr. 1.18, with an equal bulk of water, slows down the oxamid formmg reaction some 120 fold, indicating that the strength of the acid properties is not of primary importance in the oxamld formlng reaction, since such a solution would st1ll have over 50% of its original acidity and this supports my theory that the hydrochloric acid first added to the water is used up in combining with the water molecules until a concentrated solution is formed; and that after the afiinity of the water has been satisfied, further increase in concentration of the hydrochloric acid gives a chance for the excess acid molecules to form unstable addition products of hydrochloric acid with the cyanogen itself, which products then decompose to give the exceedingly efliclent oxamid formation.

The following remarks show the enormous importance of the opposing factors, above referred to, their relative magnitude, and how best to overcome the unfavorable ones.

(a) Temperature increase from 0 to C. lowers the solubility of cyanogen in water from about 8 volumes toabout 1.2 volumes and hence retards oxamid formation about 6-3- fold from this cause.

(7)) Temperature increases the tension of HCl from the solution by fully of an atmosphere at about 40 C. for 1.18 sp. gr. acid; thus theoretically reducing the partial pressure by about 38% while with stronger acid or a' somewhat higher temperature and with certain forms of apparatus, this opposing action becomes substantially infinite and no oxamid forms.

(0) Increase of temperature from 20 to also overcomes the serioiishopposing efi'ect under b; 2'. 6., it allowsa volatilecatalyzer,

in excess of that forming a constant boiling (f) Bypressure, cyanogen may be pressed or liquefied into the reaction mixture in such quantity that it combines with much or all the water so as to'release much or all the HCl gas from the solution. This gas can then be allowed to escape by releasing the pressure and the cycle repeated.

(9) In tubes at atmospheric pressure, it takes about 28 minutes at 20 C. to form a precipitate of oxamid while under the pressure of liquid cyanogen (4 atmospheres) at the same temperature, the time is reduced to about 7 minutes, thus showing a 1-fold increase (as it should be) by pressure alone. When the tube is shaken in water at 50 (1, the time is reduced to 40 seconds or 10-fold; chiefly by temperature effect alone. gives. about a 40-fold'increase due to temperature and pressure combined from 20 to 50- .C. and of over 200-fold, if we strengthen the acid from 1.14' to 1.22 sp. gr.

(it) If the acid of 1.18 sp. gr. is strengthened by cooling to perhaps 0 C. or lower, and saturating further with HCl gas, fuming hydrochloric acid may be obtained of about 1.22 sp.'gr., or 45% HCl, which gives double the rate of action over that given by the1.18-sp. gr. or 36% HCl. Also, by diluting the acid of sp. gr. 1.18 wit-h an equal bulk of water, we reduce the rate about 120 fold while by saturating it at about 0 C. the rate is doubled. This gives an increase of 240-fold in passing from a 16% acid to one o-f-about 45% of HCl.

Sulfuric acid, sp. gr. 1.55 and nitric acid of sp. gr. 1.33 act so slowly, if at all, that I cannot measure the action by the methods above indicated, which shows again that the mere strength of acid properties is not primarily concerned in the reaction; and the action, moreover, seems to be exerted particularly by the halogen acids. Finally I may add, that in one case, I added a small quantity of cuprous chlorid to the hydrochloric acid and apparently got increased activity. Cuprous chlorid forms an addition product with cyanogen and may hence have'acted as an auxiliary catalyzer.

In certain of the appended claims wherein by reason of the objection to the use of alternative expressions in the claims, hydrochloric acid is mentioned, it is to be understood that such expression is not to be regarded as limiting such claims specifically to said acid; since-hydrobromic acid is to all This gen into a bath of aqueous concentrated halogen acid the temperature of which is insuificient to permit the formation of appreciable quantities of oxalic acid, to form the product sought.

2. The process of producing oxamid which comprises conducting gaseous cyanogen into a bath of aqueous concentrated halogen acid the temperature of which is insufficient to permit the formation of appreciable quantities of oxalic acid, to form the product sought, said bath being maintained substantially saturated'with cyanogen during the reaction.

3. The process of producing oxamid which comprises conducting gaseous cyanogen into a heated bath of aqueous concentrated halogen acid under temperature conditions which do not permit the formation of appreciable quantities of oxalic acid to form the product sought.

4. The process of producing oxamid which comprises conducting-gaseous cyanogen into a bath of aqueous concentrated halogen acid under temperature conditions which favor the production of oxamid and agitating said bath while the gas is in contact therewith, to maintain the cyanogen saturation thereof.

5. The process of producing oxamid which comprises conducting gaseous cyanogen under pressure into an aqueous bath of catalytic material capable of combining the water present in said bath with said cyanogen to form oxamid.

6. The process of producing oxamid which comprises conducting gaseous cyanogen under pressure into an aqueous bath of halogenous catalytic material capable of combining the water present in said bath with said cyanogen to form a product substantially free from halogen of said satalytic material. h

7. The process of producing oxamid which comprises liberating gaseous cyanogen from'a cyanogen compound, and treating the so liberated gas with a concentrated halogen acid the halogen of which is normally incapable of being liberated in molecular condition in the presence of cyanogen and water under the temperature conditions of the operation, to cause said acid to catalytically combine the water present therein with the cyanogen, and replacing the sg combined Water by an amount substantially Just sufficient to continue the operation.

8. The process of producing oxamidwhich comprises electrolyzing a cyanogen compound to liberate gaseous cyanogen therefrom, collecting the latter and commingling therewith a concentrated halogen acid the halogen of which is normally incapable of being liberated in molecular condition in the presence of cyanogen and water under the temperature conditions of the operation, to saturate said acid with said cyanogen, and maintaining said acid sub stantially saturated while combining the water thereof with said cyanogen, to form the product sought.

9. The process which comprises effecting a vigorous exothermic reaction upon the water present in a mass of concentrated halogen acid, with cyanogen, while agitating said acid to maintain the same saturated with said cyanogen and maintaining the temperature of said mass within determined limits dependent upon the pressure under which the reaction is effected, the temperature being such as will avoid an outrush of gaseous acid from said mass while favoring a high content of cyanogen therein.

10. The process which comprises efl'ecting a vigorous exothermic reaction upon the water present in a mass of concentrated halogen acid, with cyanogen, while agitating said acid to maintain the same saturated with said cyanogen and maintaining the temperature of said mass within determined limits dependent upon the pressure under which'the reaction is effected, the temperature being such as will avoid an outrush of gaseous acid from said mass while favoring a high content of cyanogen therein, the upper temperature limit being established by cooling said mass during the progress of said oxothermic reaction.

11. The process which comprises eifecting a vigorous exothermic reaction upon the water present in a mass of concentrated halogen acid, with cyanogen, while agitating said acid to maintain the same saturated with said cyanogen and maintaining" the temperature of said mass within determined limits dependent uponthe pressure under which the reaction is effected, the temperature being such as will avoid an outrush of gaseous acid from said mass while favoring a high content of cyanogen therein.

12. The process which comprises efl'ecting a vigorous exothermic reaction upon the water present in a mass of concentrated halogen acid, with hot cyanogen gas, while agitating said acid .to maintain the same saturated with said cyanogen and maintaining the temperature of-said mass within determined limits dependent upon the pressure under which the reaction is'efl'ected, the temperature being such as willavoid an outrush of gaseous acid from said mass while favoring a high content of cyanogen therein.

13. The process of obtaining oxaniid which comprises efiecting a vigorous exothermic reaction upon the water present in a mass of concentrated halogen acid while maintaining the temperature of said mass substantially constant, and keeping the wa-' ter content thereof sufiiciently low to per- 75. mit said acid to act substantially solely as a catalyzer and, while thereby avoiding loss of said catalyzer, to produce a product free from halogenous impurities.

14. The process which comprises effecting a vigorous exothermic reaction under ressure upon the water present in a mass 0 concentrated halogen acid, with cyanogen, while agitating said acid to.maintain the same saturated with said cyanogen and maintain- .ing the temperature of said mass within determined limits dependent upon the pressure under which the reaction is effected, the temperature being such as will avoid an outrush of gaseous acid from said mass While favoring a high content of cyanogen therein.

15. The process which comprises efiecting a vigorous reaction upon the water present in a mass 'of aqueous concentrated halogen acid, withcyanogen to combine said water with at least one element of said cyanogen,

and supplying water to said mass, to compensate for that taken from said acid, by introducing acid of less concentration, whereby to continue thereaction.

16. The process which comprises eflecting, a vigorous reaction upon the water present in a mass of aqueous concentratedhalogen acid, with cyanogen, to combine said water with at least one element of said cyanogen, and supplying water to said mass to compensate for that taken from the acid, to prevent thelatter from being driven ofi in a gaseous form.

17. The process of combining cyanogen with water which comprises reacting upon an. aqueous solution of a catalyzer which is normally gaseous when free and which solution is more strongly concentrated than is the constant boiling mixture of water and said catalyzer,'to catalytically combine some at least of the water, in which is dissolved said catalyzer, with said cyanogen. 18. The process of combining cyanogen with water which comprises holding a large 12W excess of a volatile catalyzer in water by pressure and reacting catalytically upon said water with cyanogen to fgrm a product which is substantially insoluble in said water and catalyzer. I

19. The process of obtaining a substantially pure catalytic substance which comprises subjecting an aqueous solution of a volatile catalyzer to a determined pressure while combining water of said solution with cyanogen through the instrumentality of said catalyzer, to concentrate said'solution, effecting a lowering of said pressure to permit of the volatilization of a part of said catalyzer, and continuing to react upon the now more dilute solution with cyanogen at a pressure above that at which said volatilization of cat-alyzer occurred.

20. The process of producing substantially chemically pure and very highly concentrated halogen acid which comprises reacting with cyanogen upon an aqueous concentrated halogen acid, to combine the water present in said acid with said cyanogen to form oxamid.

21. The process of producing substantially chemically pure and very highly concentrated hydrochloric acid which comprises reacting upon aqueous concentrated hydrochloric acid with cyanogen at a temperature and under. pressure conditions corresponding thereto which efiects the combination of the aqueous content of said acid with said cyanogen to form substantially only oxamid.

22. The process of producing gaseous hydrochloric acid which comprises r acting upon aqueous concentrated hydrochloric acid with cyanogen to form cyamid and more highly concentrate said acid, removing a portion of the acid in gaseous form, and reconcentrating the remaining less concentrated acid by continuing the treatment thereof with cyanogen preparatory to again removing the gaseous'acid therefrom.

23. The process of producing absolute hydrochloric acid which comprises reacting upon aqueous concentrated hydrochloric acid with cyanogen to remove water therefrom, and then removing the acid in gaseous form from the residues of said reaction.

24. The process of producing 'hydrochloric acid which comprises reacting upon aqueous concentrated hydrochloric acid with cyanogen under pressure, to remove water from said acid, and then lowering the pressure upon the liquid under treatment to allow a portion of the acid to escape therefrom in gaseous form.

In testimony whereof I have aflixed my signature, in the presence of two witnesses.

JOHN E. BUCHER. Witnesses:

NORMAN E. HOLT, H; ELLIO'I'I Foo'rn. 

